Cross air blast circuit breaker



u v Ink 1 E I 7 Feb. 24, 1953 E SALZER CROSS AIR BLAST CIRCUIT BREAKERFiled Oct. 50, 1948 Patented Feb. 24, 1953 CROSS AIR BLAST CIRCUITBREAKER Erwin Salzer, Brookline, Mass., assignor to Allis- ChalmersManufacturing Company, Milwaukee, Wis., a corporation of DelawareApplication October 30, 1948, Serial No. 57,577

11 Claims. (01. 200-148) My invention relates to gas blast circuitbreakers for interrupting high alternating currents, and moreparticularly air blast circuit breakers.

t has been found that extinction of high current arcs can be achievedmost efficiently where the arc incident upon separation of a pair ofrelatively movable contacts is moved by an arc-extinguishing blast ofgas against an arc-restraining barrier of insulating material. In suchan arrangement the arc is caused to form two loops, i

one on each side of the arc-restraining barrier. The interruptingefiiciency of such a structure is probably primarily due to the factthat the gas blast acts on a plurality of arc loops and that the portionof the are which is urged by the blast into engagement with thearc-restraining barrier is effectively deionized by surface actionthereof. That surface action can be enhanced by making thearc-restraining barrier of an insulating material, preferably of organicnature, evolving 1 large amounts of gases or vapors when exposed to theheat of the arc, resulting in cooling and dilution of the arc streaminto which they are caused to diffuse.

These advantageous features are, however, in part ofiset by the factthat the arc length is rapidly increased by the arc-extinguishing blastduring the time elapsing between arc initiation and are extinction. Thatrapid increase of the length of the are results in an increase of thetotal arc energy or switch energy defined by the equation wherein ea isthe arc voltage which increases as the arc length increases, is the arccurrent and T the time of arc extinction.

It is therefore one object of my invention to provide a circuit breakerof the gas blast type wherein the surface action of an aro restra-iningbarrier of insulating material plays a major part in the interruptingprocess and wherein the length of each of the two arc loops which areformed on opposite sides of the arc-restraining barrier is limited, thuslimiting the total are energy involved in the process .of circuitinterruption.

It has been found that extinction of arcs in gas blast circuit breakerscan .be considerably facilitated by the provision of probe electrodesand resistors for shunting predetermined arc sections. If the ohmicvalue of such a shunt resistor ,is small compared to the resistance ofthe arcsecr tion which is shunted by it, a relatively large portion ofthe arc current flows through the shunt resistor and the resultingdecrease of current in the shunted arc section is correspondingly high.The arc section carrying but a small portion of the total are current isthen rapidly extinguished under the action of the gas blast. Uponextinction of such an arc section the resistor is serially related tothe remaining portion of the arc, thus limiting the arc current.

The smaller the ohmic value of a shunt resistor, the easier it is toextinguish by the blast of gas the section of the are which is shuntedby the resistor, but the less eifective is the action of the resistorwhen it is subsequently arranged in series with the remaining portion ofthe arc. Conversely, where the ohmic value of a shunt re sistor isrelatively large, the resulting decrease of current in the shunted arcsection is relatively small, and hence it is relatively dificult toextinguish the shunted section of the are by the blast of gas. Wheneverthis can be achieved the resistor, which is then serially related to theremaining portion of the arc, will be relatively effective owing to itsrelatively high ohmic value.

It is thus apparent that provision of shunt resistors having either arelatively low ohmic value, or a relatively high ohmic value, is subjectto serious limitations.

It is therefore another object of my invention to provide a circuitbreaker of the gas blast type permitting insertion of a relatively largetotal amount of resistance into the circuit in two consecutive stepseach involving but a relatively small amount of resistance wherein eachsuch step comprises elimination, by a shunt resistor, of one of the arcsections, relatively remote from the surfaces of the arc-restrainingbarrier, of the two are loops situated on opposite sides of saidbarrier, and wherein a residual or low current are extendingtransversely across the upstream end of the arc-restraining barrier isallowed to subsist until after elimination of said sections of the arc,and wherein said residual are extending transversely across the upstreamend of the arcrestraining barrier forms the portion of the arc last tobe extinguished by the blast.

In gas blast circuit breakers wherein the arc is moved against anarc-restraining barrier and is lapped around it by a blast of gasdirected substantially transversely to the direction of contactseparation, the arcing zone at the time of arc extinction is situatedfar downstream from the point where the arc was initiated. Metal vaporswhich are evolved from the hot arc terminals and electrons which areemitted from the .arc terminal forming the cathode of the arc dischargeare transferred by the blast in down- 3 stream direction into the arcingzone and greatly impair the dielectric recovery thereof.

It is therefore another object of my invention to provide a circuitbreaker of the cross-gas-blast type precluding or greatly limitingcontamination of the downstream arcing zone by metal vapors evolved fromand electrons emitted from any are terminals situated upstream from thearcing zone.

-In gas blast circuit breakers comprising an arc chute wherein the arcis moved against an arc-restraining barrier and lapped around it by anarc-extinguishing blast of gas directed substantially transversely tothe direction of contact separation, the amount of ionization within thetwo blast passages located on opposite sides of the arc-restrainingbarrier depends, among other factors, upon the length of the arc loopwithin each passage and upon the number of arc roots or arc terminalslocated in each passage or upstream of the passage and feeding arcproducts into the passage. Under otherwise similar conditions, theamount of ionization within each blast passage tends to be the smaller,the shorter the length of the arc loop within the passage.

type wherein portions of the arc loops formed on opposite sides of thearc-restraining barrier are eliminated in the early stages of theinterrupting process, resulting in a shortened arc path which is beingdeionized to the point of final arc extinction in the ultimate stages ofthe interrupting process without being seriously contaminated byevolution of metal vapors and by thermionic emission from any areterminal located at any point upstream from the arc path.

The are in a cross-gasblast circuit breaker comprises two criticalportions. One of these portions is the arc section situated immediatelyadjacent the stationary contact where there is a cloud of metal vaporsevolved and of electrons emitted from the stationary contact. The otherof these portions is the arc section situated immediately adjacent themovable contact where the atmosphere is likewise electricallycontaminated. This second critical portion is situated closest to theopening provided in the arc chute for withdrawal therefrom of themovable contact, and the hot are products resulting from that secondcritical portion of the are have a certain tendency to leak out from thearc chute through said opening.

lit is therefore another object of my invention to provide a circuitbreaker of the cross-gas-blast type wherein the arc is eliminated inthree consecutive steps comprising elimination of the section of the areimmediately adjacent the stationary contact, subsequent elimination ofthe section of the are immediately adjacent the movable contact, andfinally elimination of an intermediate substantially V-shaped arcsection ex tending from one side of the arc-restraining barriertransversely across the upstream edge portion thereof to the other sideof the arc-restraining barrier.

In a gas blast circuit breaker wherein the combined action of thearc-extinguishing blast and of the arc-extinguishing structure issufficiently effective in building up the dielectric strength of the arcgap after current zeros to preclude any subsequent gap breakdown by therising recovery voltage, there is relatively little need to rely on theinsertion of resistance into the circuit during the interruptingprocess. In such cases resistance switching may be considered as asafety factor rather than a vital feature of the circuit breaker. Undersuch circumstances resistors can be used which have a relatively smallohmic value which, in turn, minimizes .possible failure of propertransfer of the arc current to the resistor.

It is therefore one of the objects of my invention to provide a circuitbreaker of the gas blast type having one or more shunting resistors theresistances of which are sufficiently low to efiect rapid and reliableextinction of the respective arc section which is shunted by them andwhich circuit breaker has a large inherent interrupting capacitysuflicient to clear shout circuit currents though not very much reducedby previous in sertion of resistance into the circuit.

Further objects and advantages of my invention will become apparent as[the following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming pant of this specification.

Referring to the drawings,

Fig. 1 is an elevational, sectional view taken along plane 1-1 of Fig. 2of a medium high voltage cross-air-blast circuit breaker embodying myinvention in the closed circuit position thereof;

Fig. 2 is a cross-section along the plane II--II of Fig. 1;

Fig. 3 is a cross-section along the plane IIIIII of Fig. 1; and

Fig. 4 is a cross-section along the plane IV-IV of Fig. 1.

The circuit breaker comprises essentially relatively movable contacts Iand 2. The stationary contact I is formed by finger contacts and themovable contact 2 is a substantially sickle shaped blade contact.Stationary contact I is connected to terminal 3 and movable contact 2 isconnected to a terminal not shown in the drawing. Movable contact 2 ishingedly supported at 4. Hinge structure 4 may be adapted to carrycurrent from the terminal member not shown to blade contact 2. Operatinglever 5 is hinged at 6 to contact blade 2. Pulling lever 5 in a downwarddirection results in rotation of blade contact 2 in a clockwisedirection about hinge 4 and disengagement of contact 2 fro-m contactfingers I. Pushing lever 5 in an upward direction results in a similarcounterclockwise rotation of blade contact 2 and engagement of bladecontact 2 by contact fingers I.

Blast tube I connects the arc chute which has been generally indicatedby reference sign 8 with a tank (not shown) wherein a supply of areextinguishing gas as, for instance, compressed air at a pressure rangingfrom 150-250 lbs. per square inch, is stored. Arc chute 8 comprises afront plate 9a, a back plate 9?), side plates I0 and a nozzle member II. Nozzle member II is made of an insulating material that evolvesrelatively large amounts of gaseous products when exposed to the heat ofthe are as, for instance, hard fiber. Nozzle member II may be moulded,if desired, from a. compound consisting of a mixture of cement andasbestos. Such a nozzle member will evolve fairly large amounts ofgaseous products when exposed to the heat of the are, the amount or gasevolved being, however,

smaller than in the case or a nozzle member made of fiber or of asuitable synthetic resin as, for instance, a carbamide resin. A pair ofarc runners or are horns l2, I3 is arranged at the entrance or nozzle Ha little downstream from the downstream "edge of blade contact 2. Archorns l2 and I3 are aligned the direction of se aration or contacts 1and z and arranged on opposite sides of nozzle member H. Their pur poseis to cause rapid movement of any are which is drawn btwh contacts 4 and2 into nozzle passage H which is defined by nozzle member H.

As can best be seen from Fig. 2, the area ex posed to now of nozzlemember it increases all the way from intake I5 to outlet Ii. Fig. 1shows that the rate or increase of the area exposed to flow orcross-section or passage H is much larger toward outlet is than close toinlet l5.

It will be observed that passage l1 defined by blast tube 1 and passagel4 defined by nozzle member II are coaxial, while the arc extinguishing'blast through passages I! and i1 is directed transversely to thedirection of separation of contacts I and 2.

The are products which are formed within nozzle passage H are cooled ina chamber 18 situated downst'rcamlrom passage H.

Nozzle portion ll has a relatively small average area exposed to ilow,and the entrance or inlet l5 and the exhaust or outlet IG thereof arespaced a relatlvely small distance apart from each other. Coolingchamber l-B has a relatively large area exposed to flow, and an entranceporti-on l9 and an exhaust portion 20 which are spaced a relativelylarge distance apart from each other.

The arc-restraining barrier 2| of heat-resisting insulating material isarranged in cooling chamber i8 and protrudes into nozzle passage lldefined by nozzle member ll. Barrier 2| is arranged transversely to thedirection of separation of contacts I and 2. The upstream end of barrier21 is formed by a member 22 of organic insulating material which evolverelatively large amounts of gas when "exposed to the heat or the are, e.g. hard fiber. It will be noted that the po'rtiofi'of member 22 enga edby the are increases in width in doamstream direction to pro the are andmember 22. Member :22 is provided with a groove 2-3 receiving theplate-shaped portion of barrier 21 which :subdivldes cooling chamber IBinto two separate passages 28, 25. The plate-shaped portion of barrier2| and the upstream barrier member '22 are secured together by means ofpins 26 which are made of insulat ing material as, for instance, hardfiber. The upstream arc-receiving edge or barrier 21 is provided with ashallow notch 21 which tends to prevent lateral movement of the sectionof the are which is lapped around member '22 or barrier 2|. Member 22 ofbarrier 2| is secured to nozzle member H by means of pins 28, as canbest be seen in Fig. 2. y

Single probe electrodes 29 andco are arranged on opposite sides ofbarrier 21 and barrier member 22, respectivel Probe electrodes '29 30are so insulated from "each other as to be capable to be at asufli'ciently different potential to form terminals Eior an areextending 'therebe'tween. Probe electrodes :29 and 8-0 are fiormed "byplates arranged substantially transversel to the aroextinguishing blastand having arc-engaging edges which project :into home passage ll. The

are terminals formed on probe electrode plates 23, 30 have a certaintendency to move to the downstream surfaces of said plates, 1. e. theirsurfaces which are not exposed to the blast. The are terminals will staythere, until complete and final extinction of the arc has been achieved,since they are precluded from moving in downstream direction. It istherefore apparent that the terminal-forming points of probe electrodes29 and 30 are located downstream from the upstream end of barrier 2|, 1.e. downstream from the upstream end of barrier member 22. On the otherhand, the terminal-forming points of probe electrodes 29 and 30 arelocated upstream from the downstream end or exhaust 16 of nozzle passage14.

Probe electrodes 29 and are born [2 are connected by a shunt 3|.Similarly, probe electrode 30 and are horn [3 are connected by a shunt32.

Shunts 3| and 32 may have virtually zero resistance, or one of them mayhave virtually zero resistance while the other may be constituted by aresistor having an appreciable resistance, or both of them may beconstituted by resistors having an appreciable judiciously selectedresistance. The operating characteristics of the circuit breaker differdepending upon which of the above alternatives is being adopted, anddepending upon which ohmic value, or ohmic values, is being given to oneor both of the resisters. This affords a great flexibility which can beachieved with a minimum of changes.

Arc horn I2 is conductively connected to stationary finger contacts I.In a similar way, arc horn I3 is conductively connected to movable bladecontact 2. The conductive connection between arc horn l3 and bladecontact 2 comprises a metallic irame structure 33 supporting sets ofcontacts 34 arranged on opposite sides of and engaging blade contact 2.

Stacks 35, 36 of spaced metal plates are arranged in passages 24 and 25,respectively, for increasing the rate of cooling of the products ofarcing flowing past said stacks. Stack 35 is 'condu'otively connected byconductor 31 to probe electrode 29 and by shunt 3| to stationarycontact 1. Similarly, stack 36 is conductively connected by conductor 38to probe electrode 30 and by shunt 32, frame 33 and contacts 34 tomovable blade contact 2. Conductors 3! and 38 constitute evidently asecond pair of shunts in addition to the pair of shunts 3|, 32.

The are formed upon separation of contacts I and 2 is urged into nozzlepassage M by a blast of gas rushing through blast tube I. The arcterminal formed on the stationary contact finger situated farthestdownstream and projecting farthest into the blast is immediatelytransferred to are horn l2. The other are terminal which is formed onblade contact 2 is moved to the right, as viewed in Fig. 1. As soon asthe arc loop engages probe electrode 29, the section of the arcextending between arc horn l2 and probe electrode .29 will be shunted,and rapidly extinguished hereafter. Vaporization of the metal of whichare horn i2 is made and emission of electrons from arc horn 12 arestopped almost instantly upon transfer of the entire arc current toshunt 3i and probe electrode 29. From then on probe electrode 29 formsone of the terminals of the main are which extends from probe electrode29"transversely across barrier member 22 to movable blade contact 2which forms the other are terminal. As soon as the arc loop on the rightside of barrier member 22, as viewed in Fig. 1, engages both arc horn |3and probe electrode 39, the section of the arc shunted by shunt 32 tendsto become unstale and will be rapidly extinguished thereafter by thearc-extinguishing blast.

Upon shunting and extinction of the arc section extending between archorn l3 and probe electrode 30, the current path through the circuitbreaker is as follows: terminal element 3, stationary finger contacts l,are horn l2, shunt 3| and probe electrode 29. The gaseous current pathbegins at the arc termianl on probe electrode 29 and extends from therein upstream direction, then transversely across the arc-restraining edgeof barrier 2| or barrier member 22, respectively, and then in downstreamdirection to probe electrode 30, where the second portion of themetallic current path begins. That portion includes probe electrode 30,shunt 32, metal frame 33, stationary contacts 34 and sickle shaped bladecontact 2. Complete interruption of the circuit is achieved when thesection of the are extending between probe electrodes 29 and 30 has beenextinguished. This section of the arc is particularly vulnerable becauseit is subjected to the combined action of the arc-extinguishing blastand to the flow of gaseous products which are evolved under the heat ofthe arc from member 22 of barrier 2|. Moreover, and this is particularlyimportant, there is no arc root or are terminal situated at any pointupstream from the section of the arc extending between probe electrodes29 and 30 and lapped around member 22 and, therefore, there is noprecontamination of the blast which acts upon that are section byproducts of arcing formed at any upstream arc root or are terminal.Since the section of the arc which is lapped around member 22 issituated upstream from the arc roots or are terminals formed on probeelectrodes 29 and 30, contamination of that are section by products ofarcing formed on either arc root or are terminal is minimized. Electronswhich are emitted from either of both probe electrodes 29, 30 aresubject to a strong tendency to fiow with the arc-extinguishing blast ina downstream direction and out of passage l4 into cooling chamber l9,rather than against the arc-extinguishing blast in an upstream directiontransversely across member 22 and thence to the other probe electrode.Owing to these facts the dielectric recovery along the upstreamwedge-shaped end of barrier 2| will be relatively rapid, resulting ingreat interrupting eiiiciency.

It has been pointed out above that the probe electrodes 29 and 30 mustbe insulated from each other in such a way as to cause the path of leastresistance of any are section interconnecting said probe electrodes toextend transversely across the upstream edge of barrier 2|. If pins 26were made of metal rather than insulating material, this is likely tocause such lowering of the insulation level between probe electrodes 29and 30 and such change of the electric field or potential distributionbetween said probe electrodes that the path of least resistance of anyare section interconnecting probe electrodes 29 and 30 would extend fromprobe electrode 29 to the left end of one of the pins 26 and from theright end thereof to probe electrode 30. Therefore, if pins 26 were madeof metal, the section of the arc lapped around the upstream edge portionof member 22 would be shunted by two serially related arcs, oneextending from probe electrode 29 to one of pins 26 and the other fromthe one of pins 26 to probe electrode 30. This would result inunstability and rapid extinction of the arc section lapped transverselyacross the upstreamedge of member 22. Upon extinction of that aresection the current would be carried solely by the two serially relatedarcs from probe electrode 29 to pin 26 and from pin 26 to probeelectrode 30. Extinction of these two arcs would involve ratherunfavorable conditions as virtually complete elimination of thedeionizing surface action of barrier member 22 and an increase of thenumber of arc terminals from two to four and consequent contamination ofthe zones of both arcs by metal vapors and other are products formed atpoints situatedupstream from the arcing zones of the two arcs. Theproper insulation level between probe electrodes 29, 30 is, therefore, acrucial factor and an undue reduction of the insulation level betweensaid probe electrodes will materially effect the mode of operation andthe interrupting efficiency of the circuit breaker.

In order to obtain the desired operating characteristics, including anarc section last to be extinguished extending transversely across theupstream edge portion of the arc-restraining insulating barrier 2|, thatbarrier should extend from nozzle member II to a considerable length indownstream direction. The length of barrier 2| must be suflicient topreclude a transfer of the arc section which is urged by thearc-extinguishing blast into engagement with the upstream edge ofbarrier 2| to and transversely across the downstream edge thereof.

Assuming that there is a sufficiently high insulation level between theprobes 29 and 30 but that, for one reason or another, the arc sectionlast to be extinguished extending transversely across member 221sallowed to subsist for some time. Under such conditions, the two blastsof gas on either side of nozzle passage l4 will'cause continuedelongation of the arc. If sufiicient resistance has been introduced intothe circuit by means of shunts 3| and 32, as should normally be done,continued arc elongation is not likely to result in excessive arcenergy. But where the ohmic value of shunts 3|, 32 is very small, thearc should not be allowed to elongate freely. Shunts 31 and 38 areprovided for limiting the elongation of the arc section extendingbetween the probe electrodes 29 and 30 and being lapped transverselyacross barrier member 22. When the arc-extinguishing blast on the leftside of nozzle passage l4 causes the arc to loop until it engages thestack 35 of cooling plates, the section of the are extending betweenprobe electrode 29 and stack 35 will be short-circuited by shunt 31 andthus instantly eliminated. This results in a transfer to stack 35 of theterminal of the are which was heretofore on probe electrode 29.Similarly, when the arc-extinguishing blast on the right side of nozzlepassage |4 causes the arc to loop until it engages stack 36 of coolingplates, the section of the arc extending between probe electrode 30 andstack 36 will be short-circuited by shunt 39 and thus instantlyeliminated. This results in a. transfer to stack 36 of the terminal ofthe are which was here-' The longer an arc section is allowed to persist9. in a circuit breaker, the more difficult it may be to extinguish itthereafter. For this reason it might prove to be desirable in a givenapplication to provide shunt 31 in addition to shunts 3| and 32, whileshunt 38 may be dispensed with.

Where the ohmic values of shunts 3i and 32 are not too small to limitshort-circuit currents to an appreciable extent, shunt 31 may likewisebe dispensed with.

Provision of shunts 31 and 38 results in that a relatively high voltageprevails across barrier 2| after circuit interruption has been achieved.Hence it is necessary to take precautions to preclude at any time anyelectric breakdown across barrier 2|. Since this entails additionalexpense, it is optional to dispense with at least one of shunts 31 and38.

While I have illustrated and described as a preferred embodiment of myinvention a circuit breaker wherein the nozzle portion and the coolingchamber are clearly distinguishable from each other, it will be apparentthat my invention is likewise applicable to circuit breakers comprisingarc chutes of fish-tail shape wherein the nozzle portion mergesgradually into the cooling chamber.

Although but one embodiment of the present invention has beenillustrated and described, it

will be apparent to those skilled in the art that various modificationsand changes may be made therein without departing from the spirit of theinvention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A gas blast circuit breaker for interrupting high currents inalternating current circuits comprising a pair of relatively movablecontacts for drawing an arc therebetween upon separation thereof; anozzle structure of insulating material arranged adjacent said contactssubstan-- tially transversely to the direction of contact separation;means for producing an arc-extinguishing blast of gas transverselyacross the gap formed upon separation of said contacts and axiallythrough said nozzle structure; means defining a cooling chamber arrangeddownstream from said nozzle structure for receiving the blast escapingfrom said nozzle structure, the average cross sectional area of saidcooling chamber being large compared to the average cross sectional areaof said nozzle structure and the length of said cooling chamber beinglargecompared to the length of said nozzle structure; an arc-restrainingbarrier of heat-resistant insulating material arranged transversely tothe direction of contact separation and projecting from said coolingchamber into said nozzle structure; a pair of arc horns aligned in thedirection of contact separation each arranged on opposite sides of saidnozzle structure for causing .rapid movement of said are into saidnozzle structure; a pair of probe electrodes each on an opposite side ofsaid barrier downstream from the point thereof situated highestupstream; a pair of shunts each connecting one of said pair of contactsand one of said probe electrodes for eliminating the sections of the areon opposite sides of said barrier relatively remote from the surfacesthereof while an arc section extending between said probe electrodesstill persists, at least one of said pair of shunts being formed by aresistor for inserting resistance into the circuit under interruptionprior to complete ex- 10 tinction of said arc, and means for insulatingsaid probe electrodes from each other in such a way as to cause the pathof least resistance of any are section formed between said pair of probeelectrodes to extend transversely across the upstream end of saidbarrier.

2. In a gas blast circuit breaker for interrupting high currents inalternating current circuits, a pair of relatively movable contacts fordrawing an arc therebetween upon separation thereof; means for producingan arc-extinguishing blast of gas adjacent said pair of contactssubstantially transversely to the direction of contact separation; anarc chute comprising a nozzle portion arranged substantiall in thedirection of said blast and a chamber for cooling the are productsescaping from said nozzle portion, said nozzle portion having arelatively small average area exposed to flow and an entrance portionand an exhaust portion spaced a relatively small distance apart fromeach other, and said cooling chamber having a relatively large averagearea exposed to flow and an entrance portion and an exhaust portionspaced a relatively large distance apart, from each other; anarc-restraining barrier of heat-resistant insulating material in saidcooling chamber protruding into said nozzle portion and arrangedtransversely to the direction of contact separation, the portion of saidbarrier engaged by said are increasing in width in downstream directionto provide an effective surface of interaction between said are and saidbarrier; a pair of arc runners each connected to one of said contactsand extending into said nozzle portion to transfer said are from saidcontacts into said nozzle portion, the downstream ends of said arerunners being situated within said nozzle portion upstream from saidchamber for cooling the are products and upstream from the upstream edgeportion of said barrier, the only metal parts arranged in said nozzleportion in addition to said are runners being single probe electrodes onopposite sides of said barrier, said probe electrodes being so insulatedfrom each other as to be capable to be at a diilerent potential to forma pair of terminals for an are extending therebetween, theterminal-forming points of said probe electrodes being locateddownstream from the upstream end of said barrier; a pair of shunts eachconnecting one of said pair of contacts to one of said probe electrodesfor causing extinction of the sections of said are situated immediatelyadjacent said pair of contacts prior to extinction of the section ofsaid are extending between said probe electrodes; and means for sodistributing the potential across the gap formed between said probeelectrodes as to cause the arc path of least resistance therebetween toextend transversely across said upstream end of said barrier to precludeformation of any other current path across said gap.

3. In a gas blast circuit breaker for interrupting high currents inalternating current circuits, a pair of relatively movable contacts fordrawing an arc therebetween upon separation thereof; means for producingan arc-extinguishing blast of gas adjacent said pair of contactstransversely to the direction of contact separation; an arc chutecomprising a nozzle portion arranged substantially in the direction ofsaid blast and a chamber for cooling the are products escaping from saidnozzle portion, said nozzle portion having a relatively small averagearea eX- posed to flow and an entrance portion and an exhaust portionspaced a relatively small distance apart from each other, and saidcooling chamber having a relatively large average area exposed to flowand an entrance portion and an exhaust portion spaced a relatively largedis tance apart from each other; a single arc-restraining barrier ofheat-resistant insulating material in said cooling chamber protrudinginto said nozzle portion and arranged transversely to the direction ofcontact separation; a pair of arc runners each connected to one of saidcontacts and extending into said nozzle portion to transfer said arcfrom said contacts into said nozzle portion, the downstream ends of saidare runners being situated within said nozzle portion upstream from saidchamber for cooling the are products and upstream from the upstream edgeportion of said barrier; a pair of probe electrodes each arranged on anopposite side of said barrier transversely to the direction of saidblast between said entrance portion and said exhaust portion of saidnozzle at a point located downstream from the upstreamend of saidbarrier, said pair of probe electrodes being insulated from each otherin such a wa as to cause the path of least resistance of any are sectioninterconnecting said pair of probe electrodes to extend transverselyacross said upstream end of said barrier; and a pair of shunts eachconnecting one of said pair of contacts to one of said pair of probeelectrodes.

4. An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, an arc restraining insulating barrier arrangedsubstantially edgewise with respect to said arc, means for producing anarc extinguishing blast of gas substantially transversely to thedirection of contact separation, are runners arranged adjacent saidcontacts and conductively connected thereto for transferring said arefrom the region of arc initiation to a point downstream therefrom, apair of probe electrodes arranged on opposite sides of said barrierdownstream from said are runners and from the upstream edge of saidbarrier, said probe electrodes being insulated from each other in such away as to cause the path of least resistance of any are sectioninterconnecting said probe electrodes to extend transversely across saidupstream edge of said barrier, and a pair of shunts each connecting oneof said are runners and one of said probe electrode for eliminating thesections of the are situated on opposite sides of said barrierrelatively remote from the surface thereof.

5. An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, an arc restraining insulating barrier arrangedsubstantially edgewise with respect to said are, means for producing anarc extinguishing blast of gas substantially transversely to thedirection of contact separation, arc runners arranged adjacent saidcontacts and conductively connected thereto for transferring said arefrom the region of arc initiation to a point downstream therefrom, apair of probe electrodes arranged on opposite sides of said barrierdownstream from said are runners and from the upstream edge of saidbarrier, said probe electrodes being insulated from each other in such away as to cause the path of least resistance of any arc sectioninterconnecting said probe electrodes to extend transversely across saidupstream edge of said barrier,

and a pair of shunts each connecting one of said are runners and one ofsaid probe electrodes for eliminating the sections of the are situatedon opposite sides of said barrier relatively remote from the surfacethereof prior to extinction of the section of the arc extending from oneof said probe electrodes in upstream direction to and transverselyacross said upstream edge of said barrier and thence in downstreamdirection to the other of said probe electrodes.

6. An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, a nozzle structure of insulating material arrangedadjacent said contacts transversely to the direction of contactseparation, means for producing an arc extinguishing blast of gassubstantially transversely across the gap formed upon separation of saidcontacts and axially through said nozzle structure, an arc restrainingbarrier of heat resistant insulating material ar-' ranged transverselyto the direction of contact separation and projecting into said nozzlestructure, arc runners arranged adjacent said contacts and conductivelyconnected thereto for transferring said arc from the region of arcinitiation to a point within said nozzle structure, a pair of probeelectrodes on opposite sides of said barrier downstream from the pointthereof situated highest upstream, a pair of shunts each connecting oneof said arc runners and one of said probe electrodes for eliminating thesections of the are on opposite sides of said barrier relatively remotefrom the surfaces thereof while an arc section extending between saidrobe electrodes still persists, at least one of said shunts being formedby a resistor for inserting resistance into the circuit underinterruption prior to complete extinction of said are, and means forinsulating said probe electrodes from each other in such a way as tocause the path of least resistance of any are section formed betweensaid probe electrodes to extend transversely across the upstream end ofsaid barrier, said insulating means including the dielectric integrityof said barrier.

7. An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, means for producing an arc extinguishing blast ofgas adjacent said contacts substantially transversely to the directionof contact separation, an arc chute comprising a nozzle portion arrangedsubstantially in the direction of said blast and a chamber for coolingthe are products escaping from said nozzle portion, said nozzle portionhaving a relatively small average area exposed to flow and an entranceportion and an exhaust portion spaced a relatively small distance apartfrom each other, and said cooling chamber having a relatively largeaverage area exposed to flow and an entrance portion and an exhaustportion spaced a relatively large distance from each other, an arcrestraining barrier of heat resistant insulating material in saidcooling chamber protruding into said nozzle portion and arrangedtransversely to the direction of contact separation, arc runnersarranged adiacent said contacts and conductively connected thereto fortransferring said are from the region of arc initiation to a pointwithin said nozzle, single probe electrodes arranged on opposite sidesof said barrier downstream of said are runners, said probe electrodesbeing so insulated from each other as to be capable of being atdifferent potentials to form a pair of terminals for an arc extendingtherebetween, the terminal forming points of said probe electrodes beinglocated downstream from the upstream end of said barrier and upstreamfrom the downstream end of said nozzle, and a pair of hunts eachconnecting one of said are runners to one of said probe electrodes.

8. An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, an arc chute for receiving said are, a singleinsulating barrier arranged within said are chute adjacent the gapformed upon separation of said contacts, means for producing an arcextinguishing blast of gas substantially parallel to the axis of saidbarrier for driving said are against an arc restraining edge portion ofsaid barrier, are runners arranged adjacent said contacts andconductively connected thereto for transferring said are from the regionof arc initiation to a point within said are chute, a pair of probeelectrodes arranged on opposite sides of said barrier at points locateddownstream from said are restraining edge portion, a pair of shunts eachconnecting one of said contacts to one of said probe electrodes foreliminating the sections of said are situated on opposite sides of saidbarrier relatively remote from the surfaces thereof, and means forcausing the section of said are last to be extinguished by said blast toextend from one of said probe electrodes in upstream direction to andtransversely across said are restraining edge portion and thence indownstream irection to the other of said probe electrodes.

9, An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, means for producing an are extinguishing blast ofgas adjacent said contacts, an arc chute comprising an upstreamrelatively short and narrow nozzle portion arranged substantially in thedirection of said blast and a downstream relatively long and widecooling portion for reducing the temperature of the products of arcingformed within said nozzle portion, said nozzle portion having arelatively restricted inlet and a widely flaring outlet, a single arerestraining barrier of heat resistant insulating material in saidcooling chamber protruding into said nozzle portion and arrangedtransversely to the direction of contact separation, the portion of saidbarrier engaged by said are increasing in width in downstream directionto provide an effective surface of interaction between said are and saidbarrier, arc runners arranged adjacent said contacts and conductivelyconnected thereto for transferring said are from the region of arcinitiation to a point within said are chute, probe electrode means onopposite sides of said barrier consisting of a single pair of probeelectrodes separated by said barrier, said probe electrodes being soinsulated from each other as to be capable of being at differentpotentials to form a pair of terminals for an arc extendingtherebetween, the terminal forming points of said probe electrodes beinglocated downstream from the upstream end of said barrier and betweensaid inlet and said outlet of said nozzle portion, means for sodistributing the potential between said probe electrodes as to cause thearc path of least resistance therebetween to extend transversely acrossthe upstream end of said barrier, and means for shunting the sections ofsaid are extending between said are runners and said probe electrodes. I

10. An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, means for producing an are extinguishing blast ofgas substantially trans versely to the direction of contact separation,an arc chute comprising a nozzle portion arranged substantially in thedirection of said blast and a chamber for cooling the products of arcingescaping from said nozzle portion, said nozzle portion consisting of aninsulating material evolving relatively large amounts of gas whenexposed to the heat of the arc and having a relatively small averagearea exposed to flow, said cooling chamber having a relatively largeaverage area exposed to flow and by far exceeding the length of saidnozzle portion, a single arc restraining barrier of insulating materialarranged in said cooling chamber transversely to the direction ofcontact separation, said barrier being free from any metal massesexposed to arcing and having an upstream portion projecting into saidnozzle portion and being provided with an arc restraining notch, arcrunners arranged adjacent said contacts and conductively connectedthereto for transferring said are from the region of arc initiation to apoint within said nozzle, single probe electrodes on opposite sides ofsaid barrier, said probe electrodes projecting transversely across saidnozzle portion with the inner ends thereof projecting into said area ofsaid nozzle portion exposed to flow, said probe electrodes beingarranged in spaced relation from said barrier to form an air gap betweensaid barrier and each said probe electrode, said probe electrodes beingso insulated from each other as to be capable of being at differentpotentials and to form a pair of terminals for an are extendingtherebetween, the terminal forming points of each said probe electrodesbeing located in such a way as to be separated from each other by saidupstream portion of said barrier, means for so distributing thepotential between said probe electrodes as to cause the arc path ofleast resistance therebetween to extend transversely across saidupstream portion of said barrier, and a pair of shunts eachinterconnecting one of said contacts and one of said probe electrodes.

11. An alternating current circuit interrupter comprising a pair ofrelatively movable contacts for drawing an arc therebetween uponseparation thereof, means for producing an are extinguishing blast ofgas adjacent said contacts transversely to the direction of contactseparation, an arc chute comprising a nozzle portion arrangedsubstantially in the direction of said blast and a chamber for coolingthe are products escaping from said nozzle portion, said nozzle portionhaving a relatively small average area exposed to flow and an entranceportion and an exhaust portion spaced a relatively small distance fromeach other, and said cooling chamher having a relatively large averagearea exposed to flow and an entrance portion and an exhaust portionspaced relatively large distance from each other, a single arcrestraining barrier of heat resistant insulating material in saidcooling chamber protruding into said nozzle portion and arrangedtransversely to the direction of contact separation, said barrier beingfree from any metal masses exposed to arcing, arc runners arrangedadjacent said contacts and conductively connected thereto fortransferring said are from the region of arc initiation to a pointwithin said are chute, single probe electrodes on opposite sides of saidbarrier, said probe electrodes projecting transversely across saidnozzle portion with the inner ends thereof projecting into said area ofsaid nozzle portion exposed to flow, said probe electrodes beingarranged in spaced relation from said barrier to form an air gap betweensaid barrier and each said probe electrode, said probe electrodes beingso insulated from each other as to be capable of being at differentpotentials to form a pair of terminals for an are extendingtherebetween, the terminal forming points of said probe electrodes beinglocated downstream from the upstream end of said barrier and upstreamfrom the downstream end of said nozzle, and a pair of resistors eachconnecting one of said pair of contacts and one of said probeelectrodes.

ERWIN sALzER.

1 6 REFERENCES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 1,861,129 Milliken May 31, 19321,944,402 Clerc Jan. 23, 1934 2,284,842 Prince et al June 2, 19422,345,724 Baker et al. Apr. 4, 1944 2,451,669 Eichenberger Oct. 19, 19482,486,127 Davies Oct. 25, 1949

